Automatic stoking grates



M. DVIRKA AUTOMATIC STOKING GRATES Filed May 22, 1965 6 Sheets-Sheet l By M/ROSLAV DV/R/(A A T TORNE V Dec. 7, 1965 M. DvlRKA AUTOMATIC STOKING GRATES 6 Sheets-Sheet 2 Filed May 22, 1963 /N VEN TOR M/ROSLA I/ DWR/(A VI B Dec 7, .1965 M. DvlRKA AUTOMATIC STOKING GRATES 6 Sheets-Sheet 5 Filed May 22, 1963 /NVENTOR MIROSLAV DWR/(A A 7' TOR/VE V 6 Sheets-Sheet 4 Filed May 22, 1963 /A/VE/VTOR y M/ROSLAV DWR/(A *a ATTORNEY Dec. 7, 1965 M. DvlRKA 3,221,679

AUTOMATIC STOKING GRATES Filed May 22, 196s e sheets-sheet 5 F/G. 4A

/Nl/ENTOR 5y M/ROSLAV DWR/(A ATTORNEY Dec. 7, 1965 M. DVIRKA AUTOMATIC STOKING GRATES 6 Sheets-Sheet 6A Filed May 22, 1963 /N VEN To@ M/ROSLAV DWR/(A ATTORNEY United States Patent O 3,221,679 AUTOMATIC STOKING GRATES Miroslav Dvirka, Long Island City, N.Y., assigner to Morse Boulger Inc., New York, N.Y., a corporation of Delaware Filed May 22, 1963, Ser. No. 282,319 7 Claims. (Cl. 110-36) The instant invention relates to grates for the stoking of burning material in the combustion chamber of incinerators.

An important problem in the burning of material is the matter of stoking the material so as to consume it as completely and thoroughly as possible. In the prior art the burning material has generally been manually agitated to move individual portions of the burning material to other positions and locations on the grates until finally the material still not consumed is removed from the grates. While mechanical stokers are in the prior art they have the disadvantage that the burning material is propelled along the grates at more or less a uniform rate from the more intense region of burning to the peripheral combustion region, such propulsion being more or less independent of the actual consumption of the burning material in the incinerator. That is, the burning material is retained in the intense combustion region for but limited time, and then the material still not burned as much as it could actually burn if it were still at the region of intense combustion, is dumped or removed from the cornbustion chamber.

An object of my invention is to provide a stoking grate which permits of unlimited retention time on the grates of the material being burned, in which the burning material is continuously mixed and agitated in the entire area of combustion.

Still a further object thereof is to so construct a stoking grate that the burning material tends to be moved from the peripheral region of a rotating grate structure to the central region thereof, thus permitting charging the refuse at any point along the perimeter of the grates.

Still another object of my invention is to provide a stationary stoking arm above a rotating grate assembly, which arm not only tends to scoop or plow up the burning material on the rotating grate but also to throw the scooped material radially inward of the grate assembly.

The foregoing objects, as also other objects and features of the instant invention will be readily understood from the following description of an illustrative embodiment of my invention when read in conjunction with the appended drawing in which FIG. l is a top plan view of the automatic stoking grate assembly in accordance with the invention;

FIG. 2 is a section on line lI-II of FIG. 1, along the diameter of the grate assembly above which the stoker arm is spatially fixed, the Stoker arm being shown in longitudinal elevation, and partially in section at one end;

FIG. 3 is an elevational view of the support beam of the stoker of my invention, with FIG. 3 a top view thereof, and FIGS. 3B and 3C enlarged sections at lines IIIB- IIIB and lIIC-IIIC of FIG. 3B;

FIG. 4 is an elevational section through the grate dumping mechanism with only those parts of the grate assembly shown, wholly or partially necessary for an understanding of its operation, with FIG. 4A a front elevational View of the exterior portions of the dumping mechanism;

and

FIG. 5 is a top view of the stoker arm, FIG. 5A an end view thereof, and FIGS. 5B through 5E transverse sections of the stoker arm at predetermined regions thereof as indicated on FIG. 5.

Referring to the drawing, the automatic stoking grates 3,221,679 Patented Dec. 7, 1965 of my instant invention are mounted in a cylindrical casing 1 set into the wall of the incinerator so that the upper face of a grate assembly is at a substantial distance from the floor of the incinerator and adequate space is left below the grate assembly for the ash pit and the grate drive mechanisms positioned beyond the grate assembly below such face of such assembly. Casing 1 at its upper end carries cylindrical flange 2 extending both outwardly and inwardly therefrom of which the upper face mounts a pair of diametrically opposite bearings 3 in which the ends of a stoker arm 4 are mounted so that the lowermost face of the stokng arm or plow 4 is spaced a convenient distance above the upper surface of the grates. The casing may conveniently be of two or more arcuate sections which are assembled to form the casing with the ends of the sections spaced from each other as shown at 10 to allow for expansion of the cylinder on heating.

The grate assembly comprises substantially an annular channel 5 supported at its bottom face by a plurality of rollers 6 spaced about, and supported on, the interior surface of cylindrical casing 1 at spatially xed regions thereof and all at the same distance below channel 5. Gussets 7 reinforce the cylinder and extend from the exterior annular wall of cylinder 1, opposite the regions at which rollers 6 are mounted. To the interior of annular channel 5, the grate assembly includes, as a minimum, one annular grate 8 and a pair of semi-circular grates 9 at the central region of the assembly. Preferably, however, a plurality of annular grates 8 are included in the grate assembly, my illustrative embodiment showing three annular grates, an inner grate 81, and intermediate annular grate 82, and an outer annular grate 83. The maximum number of annular grates in the plurality is limited only by economic and structural considerations. All grates are provided with a plurality of apertures 11 for passage therethrough of the ashes of the combusted material, only some of the apertures being shown in order to permit more facile understanding of the drawing. The outer annular grate 83 at its upper peripheral lateral region has a radially outwardly extending flange 12 from its outer circumferential face, which is supported by a plurality of annular spaced projections 13 projecting inwardly of the grate assembly from channel 5, while a radially inwardly projection ange 14 extends from its inner circumferential face inwardly of the grate assembly at substantially the midheight region thereof. Similarly, each intermediate annular grate 82 has a flange 15 at the upper region of its outer circumferential face extending outwardly of the grate and a flange 16 at the midheight region thereof extending inwardly of the grate. Inner annular grate 81 has flange 17 extending in the outward direction of the grate from its outer cylindrical surface of its upper end region. Flange 12 so rests on projections 13, flange 15 on flange 14, and flange 17 on flange 16, that the upper faces of all annular grates 81, 82, 83, and semicircular grates 9 are substantially co-planar.

Each of annular grates 81, 82 and 83 in turn consists of two semicircular segments 18 and 19 having radial end surfaces which are in the form of a fork 20, and are pivotally connected at such forked ends to supporting beam 21 substantially of W-shape longitudinally with horizontal extensions 22 at the upper ends of the outer arms of the W-shape with the upper surface of extensions 22 coplanar with the upper face of the intermediate portion 23 of the W-shape. Beam 21 is aixed at both its end regions to dimetrically opposite regions of channel 5 so that the linear supporting beam 21 is across a diameter thereof with the upper faces of extensions 22 and of its intermediate portion 23 coplanar with the upper faces of all the grates. For each annular grate segment 18 and 19, beam extensions 22 have a laterally extending portion 24 arranged in pairs at laterally opposite sides of the beam. Grate segments 18 and 19 are each interlocked with an individual portion 24, respectively, by a grate lock pin 25, the ends of which are circular to tit into corresponding apertures through forks 20 of the grate segments, the forks fitting about the sides of projecting portions 24. Lockpins are cylindrical their entire length and have a flat plate 26 extending therefrom at their intermediate region with one face of plate 26 on the extension of a radius of the pin, the plate or key titting into a cooperating slot in the associated semi-annular grate segment 18 or 19 and so located that with key 26 therein in vertical position the upper face of the segment is coplanar with the upper face of beam extension 22.

Supported centrally along the diameter of channel 5 along which beam 21 extends, one of a pair of axially aligned rotatable shafts 27 is supported in bearing 28 in one of beam extensions 22 and in bearing 29 in intermediate beam portion 23, while the other of shafts 27 is supported in the other bearing in intermediate beam portion 23 and in bearing 31 in the other of beam eX- tensions 22. The inner ends of shafts 27 are spaced a short distance from each other in the interval between bearings 29 and 30 in the beam intermediate portion 23.

The abutting linear face of each semicircular grate 9 has a first cut-out portion 32 at one end of the linear face which extends laterally across and above the associated one of shafts 27, an immediately adjacent first projection 33 likewise which extends laterally across and above such one shaft 27, a second cut-out portion 3 which extends over the spaced inner end regions of both axially aligned shafts 27, and a second projection which extends across the other of shafts 27. The first cut-out portion 32 of the one grate 9 accommodates the second projection 35 of the other grate, the tirst projection 33 of the one being accommodated by the second cut-out portion 34 of the other, second cut-out portion 34 of the one accommodating the first projection 33 of the other, and the second projection 35 of the one being accommodated in the first cut-out portion 32 of the other. While the width of each first cut-out portion 32 is but slightly larger than the width of each second projection 35, the width of each second cut-out portion 34 is considerably larger than the width of each rst projection 33, so that at the mid-region of the assembled semi-circular grates 9, below which the inner ends of axially aligned shafts 27 are spaced, an aperture is formed into which the intermediate portion 23 of the W-shaped beam 21 extends with its upper surface substantially coplanar with the upper face of the grates. It will be noted from FIGS. 1 and 5 that the central region (compare FIG. 5D) of stoker arm 4 is spaced above such aperture.

Integral with the lower face of the first and second projections 33 and 35 of each semicircular grate, eyes 36 and 37, integral therewith, are keyed, respectively, to the one of aligned shafts 27 passing therethrough to such one shaft so that each grate 9 can be rotated from its horizontal position to its substantially vertical dumping position when the shaft 27 keyed thereto is rotated. To rotate each shaft 27 in the dumping direction, there is provided for each of shafts the following mechanism. A gravity latch member 38 is pivotally supported on pin 39 from the lower face of a segment 18 or 19 of the outer annular grate. The gravity latch member 38 is in the form of a hook so suspended that the hook, on rotation of the grate assembly in the predetermined direction, anti-clockwise as shown by the arrow in FIG. 1, presents a convex follower face. Obviously, as two grates 9 disposed to opposite sides of support beam 21 are to be dumped and restored, a pair of gravity latch hooks 38 is provided one to each side of support beam, preferably at opposite end regions or extensions 22 of the beam.

At the forward end region of each shaft 27 there is aflixed thereto an angular arm 40 carrying a pin 41 at its free end region and adapted normally to latch with a formed recess 42 by the concave curved region of hook 38 when the upper of face semi-circular grate 9, which the respectively respective hooks control as to dumping, is coplanar with the upper faces of the other grates of the assembly. In such latched position, the center of gravity of each hook 38 is so displaced that the moment of the relatively heavy hook is such that were the hook free to move, it would tend to hold the associated grate 9 from dumping. It will further be recalled that the entire grate assembly, including the beam 21, the annular grates 8 and the semicircular grates 9, rotates as a unit. To provide dumping of grates 9, I provide but one dumping station at which by manual control, grates 9 can be selectively operated manually during rotation of the grate assembly.

The dumping station (FIGS. 4 and 4A) comprises a housing 5t), which may be a horizontal section of pipe, is installed in the incinerator pit or wall enclosing the pit, to the exterior of cylinder 1 below the grate assembly. A shaft 51, rotatably supported in the end Walls of housing 5t) has one end 52 projecting beyond the outer face of the incinerator wall, a hand lever 53 being attached to projecting end 52, the inner end 54 of shaft 51 has an arm 55 attached thereto of which the free end is in the form of a stirrup 56. Above shaft 51 as slide bar 57, having an external hand grip 58, is supported in housing 5t) and has an arm portion S9 on the region within the ash pit, arm portion 59 extending linearly in an upward angular direction parallel to arm 55 of shaft 51. At its free end region portion 59 carries a shaft 60 extending at right angles therefrom toward and through aligned apertures in the side walls of stirrup 56, shaft 60 extending beyond the stirrup 56 so that when the slide bar 57 is pushed inwardly as far as it will go, such extending portion of shaft 60 is in the rotary path of hooks 38, while when slide bar 57 is pulled outwardly shaft 60 is out of such rotary path. Within the stirrup 56, a roller 61 is freely rotatable on shaft 60 and is so positioned vertically and laterally that while it engages dump arm 40 when slide bar 57 is in an inwardly pushed position, the latter arm can pass the roller 61 with a rolling action of the roller. It will also be noted that since the lower end of handle 53 is attached to rotatable shaft 51 below the slide bar, an elongated arcuate groove 64 is provided through the end wall of housing 50 through which slide bar 57 extends to allow for manual movement of handle 53 both in the given direction to move the roller supporting shaft 60 laterally and upwardly in the rotary path of hooks 38 so that the respective latching pins 41 will disengage from the hooks successively as the grate assembly rotates. One end of the arcuate groove 64 is at a point about equal to the normal angular movement required for handle 53 from a normal position, shown in FIG. 4A in dashed lines, which in my illustrative embodiment is of the order of 30, to disengage pin 41, while the other end of the groove is preferably at more than an equal angular distance from such normal, and non-dumping, position, so that the total angular length of groove 64 is some 60 or more, in the upper left quadrant (FIG. 4B), through which hand lever 53 is movable.

Thus, when it is desired to dump the semicircular grates 9, handle 53, normally at an angle of some 30 to the vertical at about midway of groove 64 and connected to a spring 65 of an air cylinder, not further shown, one end of spring 65 being anchored to the free end region of handle 53 and its other end to a fixed spatial point, for example the bottom of the air cylinder, is manually pivoted in the predetermined direction to its vertical, dumping position, shown in full lines in FIG. 4A. This pushes slide bar 57 inwardly, so that its front stop 62 is substantially against the front wall of housing 50, and roller 61 in stirrup 54 and its shaft 60, are both moved upwardly and laterally inward into the path of the free ends of hooks 33 so that recess 42 of the hooks is disengaged from pin 41 of the dump arm 40 as the grate assembly "discussed, to restore to the preoperated position.

fot'ates and the extending remote end of roller shaft 6 strikes hooks 38 successively. With pin 41 out of recess 42, the particular semicircular grate 9,`keyed to the particular shaft 27 to which the particular dump arm 40 is also keyed is free to move under the added weight of the uncombusted and incombustible refuse thereon and swings downwardly to discharge such refuse into the ash pit. Obviously, the manually operable handle is held in its dump position and continued rotation of the grate assembly will bring the lower end of the other hook 38 into engagement with the extending remote end of shaft 60 to disengage hook recess 42 from pin 41 of its dump arm 40, unlatching the other semicircular grate 9. It will be recalled that the solid products of combustion fall through apertures 11 of the grates, and a hook 38 is so attached to associated semicircular grates 9 as yto maintain the grates horizontal, and hence if there is no uncombusted or incombustible refuse thereon they will not be dumped even though unlatched. Once the handle 53 is moved to its dumping position, it will remain there under the tension of spring 65, until the handle is either manually moved to its preoperated position or is caused by an excessive tension on spring 65, produced as will be below Where no unburned or unburnable refuse, such as metal cans, rods, etc., interferes with the restoring movement of a -semicircular grate 9 after it dumps, the grate, having emptied itself of such refuse, tends to rotate back to its normal and horizontal position thus rotating dump arm 40 in the proper direction for the lower side of pin 41 to clear the higher front region of the lower face of recess 42. However, as stated, before there can be any latching, hand lever 53 must be moved to the dumping position and the shaft 60 pulled out by means of the hand grip 58.

Now, if some obstruction prevents restoration of Ithe associated grate 9 to its normal horizontal position, thus preventing the restoring movement of dump arm 40, the dump arm 40 will exert excessive pressure on roller 61 which, in turn, will transmit the increased force to the precalibrated spring 65. The latter will thus extend allowing the dump arm 40 to pass the roller 61 in whatever position the grate is jammed. Ultimately, sufficient `reactive force is built up to remove the obstruction in every but the most extraordinary case, in which event the drive of the grate assembly would probably have to be stopped and the obstacle removed by disassembly of the structure to the extent of having to remove the grates. Such extraordinary obstruction has, in fact, not occurred and appears rather unlikely to occur. The obstacle having been removed, the semicircular grate is thus restored to its normal position with its upper surface horizontal, as above stated.

It will be recalled that the channel 5 is supported on a plurality of rollers 6, Channel 5 is conveniently of C-shape supported with its web vertical and its flanges extending horizontally outward. A roller or conveyor type chain 43 is attached, by clamping or welding, to the exterior cylindrical surface of the web of the channel 7 and meshes with gear 46 on vertical drive shaft 47 to rotate channel 5 and the grate assembly carried thereby. The vertical drive shaft is installed spatially to the exterior of channel 5 and at a level below the grate assembly, and is powered, for example, by a gear chain driven from the rotor of an electric motor (not shown). All of the driving mechanism for channel 5 is enclosed, obviously, except at the region of meshing of the driving roller chain 43 with the then adjacent teeth of drive gear 46, in a housing 48 to protect it from dirt, ashes, etc., below the grates.

The stoker arm or plow is freely supported by brackets 3 on top of flange 2 at a predetermined distance above the upper face of the grate assembly. The stoker arm is preferably of a chrome nickel alloy and extends clear across a diameter of the grate assembly in channel 5, and is of substantially S-shape in plan view with the midportion of the S-shape above the central region of the grate assembly. It is hollow in cross-section which gradually and substantially uniformly varies from right triangular at both ends to square or rectangular at its midlength, as shown in detail in the sections of FIGS. 5B through 5E, the right-angles being on opposite sides of the respective sections of the two arcuate portions of the S-shape. The leading edge 71 in the direction of rotation, as indicated by the arrow in FIG. 1, of each such arcuate portion 72 of the stoker arm is longitudinally curved in such direction that on such rotation the curvature of the leading edge tends to propel the burning material on the grate assembly toward the central region of the grate assembly. It will be noted that the leading edge 71 of the arcuate portion of the stoker shown to the left of its midregion is on the opposite side of the arcuate portion to the right of such midlength point since rotation of the grate assembly is continuous in the one direction and the stoker arm is stationary. While the exact curvature of the leading edge of the arcuate portions is not in any manner limited to that shown for my illustrative embodiment, just so long as the form of the leading edge results in the propulsion of the burning material toward the central or inner regions of the grate assembly, I have arrived at the particular curvature shown by using a horizontal reference line through substantially the midlength point of the arm and plotting and connecting in a smooth curve, successive points from a point vertically spaced from substantially one end of the reference line representing the length of my stoker arm to the midlength point thereof for both arcuate portions, each successive point being on a line making about 30 with the line through its immediately preceding point, the 30 angle being outwardly from the reference line for about the rst half of each arcuate section starting at or about the arm end and then being inwardly toward the reference line from about the middle of each arcuate section to the center of the stoker arm. The leading face 73 of each arcuate portion at the outer ends thereof is at an angle of about 45 to the lower face of the stoker arm and the upper face of the grate assembly and, proceeding in the direction to the -center of the arm length, increases, smoothly and substantially uniformly, see the sections shown in FIGS. 5B through 5E, where it is at right-angles to the stoker lower, and the grate assembly upper, surfaces. Each end portion of the stoker arm, as shown in FIG. 5A, has a transversely extending plate 74 integral with it to enable it to be slid into the slot of the Stoker arm supporting bracket or bearing 3 on flange 2. Through each bracket 3 an air supply pipe 75 supplies a continuous flow of air for both (a) combustion, and (b) cooling the Stoker arm to the bracket, the air being conducted by a sleeve 77, extending through the bracket wall a short distance into the adjacent end of the Stoker arm. Air ports 76 are provided in the arm to permit passage of the air for combustion, and are preferably disposed, as shown for example in FIG. 5B, in the trailing faces of the arcuate arm end portions. I call attention to the fact that each end portion of the stoker arm with its integral plate 74 is neither bolted nor otherwise affixed to or in brackets 3, thus allowing for expansion and contraction thereof on heating and cooling, but merely rest by the weight of the stoker arm in such brackets. Such resting of the arm ends in the brackets, permitting of some movement of the Stoker arm, will also minimize possible damage, concededly very rare and infrequent, caused by noncombusted or noncombustible masses of material of excessive dimensions and strength on the grate assembly.

On rot-ation of the grate assembly in the predetermined direction, the leading face 73 of each arcuate portion 72 of stoker arm 4 acts as a plow on the material being cornbusted Von the grate assembly, throwing all material which is higher than the predetermined distance between the lower face of the stoker larm and the grate assembly, upwardly over the stoker arm and, due to the longitudinal curvature of the leading edge 71, toward the central region of the grate assembly. On rotation of the dump shafts 27, the incombustible residue at such central region may, at intervals, be dumped into the ash pit from the semicircular grates 9 which are the most central portions of such central region.

It follows that in the operation of the automatic stoker grate assembly of my invention, portions of the material to be burned are continuously agitated and repositioned relative to other portions thereof, thus assuring excellent and as complete as possible combustion thereof, with no portions of the combustible material remaining unburned. Thus, retention time of material on the grates to be burned is not limited, and tall portions thereof that are combustible are, in fact, burned.

Not shown, or described herein, are any burners to ignite the material on the grate assembly, etc., since their types, their locations relative to the grate assembly etc., is not different from the types, locations and direction of flame, utilized with prior art grates.

It will be understood that the embodiment and the elements thereof of my invention hereinabove described in the specification and shown in the drawing are, by way of illustration, and are not limited in any way except as required by the prior art.

What I claim is:

1. An automatic stoking grate assembly comprising a casing, a plurality of grates supported within the casing with the upper faces of the grates coplanar, the plurality of grates comprising a pair of semicircular grates at the center of the plurality and at least one annular grate about the pair of semicircular grates, means for rotating the plurality of grates as a unit, a stoking arm extending diametrically across the plurality of grates immovably mounted on and above the casing and at a distance above the upper faces of the grates of the plurality and of such configuration that material to be combusted positioned on the grates is plowed up by the arm on rotation of the grate plurality and thrown over the arm in the direction toward the central portion of the upper face of the grate plurality, a diametrical support crossbeam below the grate plurality, and a pivotal connection between at least each semicircular grate and the crossbeam, each pivotal connection being coplanar with the upper face of each grate.

2. An -automatic stoking grate assembly comprising a casing, a plurality of grates supported Within the casing with the upper faces of the grates coplanar, the plurality of grates comprising a pair of semicircular grates at the center thereof and a plurality of -annular grates about the pair of semicircular grates of which each successive annular grate is about the pair of semicircular grates and about the preceding annular grate, each annular grate consisting of two half sections, means for rotating the plurality of grates as a unit, a stoking arm extending diametrically across the plurality of grates immovably mounted on and above the casing at a distance above the upper faces of the grates of the plurality and of such conguration that material to be combusted positioned on the grates is plowed up by the arm on rotation of the grate plurality and thrown over the arm in the direction toward the central portion of the upper face of the grate plurality, a diametrical support crossbeam below the pair of semicircular grates and the annular plates, the ends of the crossbeam being slidably supported on the casing, and a pivotal connection between each semicircular grate and each half section of the annular grates and the crossbeam, the upper face of each pivotal connection being coplanar with the upper face of the grate plurality.

3. The automatic stoking grate assembly according to claim 2 in which each of the annular grates consists of two half sections, the pivotal connection of each plate of the pair of semicircular plates and of each pair of half sections of the annular plates being at the adjacent ends of the respective pair of plates and the upper faces of the pivotal connections being coplanar with the upper faces of the plates of the plurality.

4. The automatic stoking grate assembly according to claim 2 having means selectively actuatable during rotation of the plurality of grates to tilt at least one of the semicircular grates to and from a position in which its upper face is inclined downwardly from the plane of the upper faces of the other grates of the plurality.

5. The automatic stoking grate assembly according to claim 2 in which means selectively actuatable during rotation of the plurality lof grates in succession engage cooperating means on the semicircular grates of the pair to permit the particular semicircular grate to tilt to its dumping position under the weight of refuse on the particular semicircular grate.

6. The automatic stoking grate according to claim 2 in which the radially outermost of the annular plates has a shoulder at its outer periphery slidably supported on the casing, and each half section of each of the annular plates from the radially outermost to the radially innermost annular plate has a peripheral extension from its lower face on its inner radial periphery for supporting the next radially inwardly adjacent annular grate plate with their upper faces coplanar with the upper faces of the central semicircular plates and the upper faces of the pivotal connections.

7. The automatic stoking grate according to claim 2 in which the Stoker arm is hollow and connected to a source of cooling liquid for circulation of the liquid therethrough.

References Cited by the Examiner UNITED STATES PATENTS 694,268 2/1902 Groll 110-36 1,43 6,437 ll/l922 Crossen -36 2,183,386 12/1939 Yeager 110-36 2,194,630 3/1940 Andrews 110-36 2,548,086 4/1951 West et al 110-36 FOREIGN PATENTS 629,015 4/ 1936 Germany.

FREDERICK L. MA'ITESON, IR., Primary Examiner.

KENNETH W. SPRAGUE, JAMES W. WESTHAVER,

Examiners. 

1. AN AUTOMATIC STOKING GRATE ASSEMBLY COMPRISING A CASING, A PLURALITY OF GRATES SUPPORTED WITHIN THE CASING WITH THE UPPER FACES OF THE GRATES COPLANAR, THE PLURALITY OF GRATES COMPRISING A PAIR OF SEMICIRCULAR GRATES AT THE CENTER OF THE PLURALITY AND AT LEAST ONE ANNULAR GRATE ABOUT THE PAIR OF SEMICIRCULAR GRATES, MEANS FOR ROTATING THE PLURALITY OF GRATES AS A UNIT, A STOKING ARM EXTENDING DIAMETRICALLY ACROSS THE PLURALITY OF GRATES IMMOVABLY MOUNTED ON AND ABOVE THE CASING AND AT A DISTANCE ABOVE THE UPPER FACES OF THE GRATES OF THE PLURALITY AND OF SUCH 